[dTal]

Well, with a 35-45 lb. annual weight gain, after 40 years you would literally weigh as much as a car. Obviously that doesn't happen with any regularity, so clearly an equilibrium is reached and the curve flattens off at some relatively modest point. Therefore, the heavier you are, the more food you need to maintain your weight. Asymptotically, calorie intake predicts your final weight, not weight gain.